Various X-ray baggage scanning systems are known for detecting the presence of contraband in baggage or luggage, prior to loading the baggage onto a commercial aircraft. In recent years there has developed considerable interest in detecting explosive materials that may be hidden in baggage. Since many explosive materials may be characterized by a range of densities differentiable from that of other objects typically found in baggage, explosives are generally amenable to detection by X-ray equipment. A common technique of measuring a material's density is to expose the material to X-rays and to measure the amount of radiation absorbed by the material, the absorption being indicative of the density.
With the tremendous growth of the travel industry, there has been a recent trend to automatically detect the presence of such explosive materials with X-rays. Different X-ray systems have been proposed. For example, U.S. Pat. No. 5,319,547 and U.S. Pat. No. 5,838,758, both issued in the names of Krug et al. and assigned to Vivid Technologies of Waltham MA (hereinafter the '547 and '758 Patents), describe an X-ray line scanner for automatically scanning luggage (hereinafter the "Vivid Machine"), while U.S. Pat. No. 5,367,552, issued to Peschmann and assigned to InVision Technologies of Foster City, Calif., describes a CT scanner for automatically scanning luggage (hereinafter the "InVision Machine").
Current Federal Aviation Agency (FAA) regulations define the requirements for certifying automated explosive detection systems and imply high sensitivity (high probability of detection) and high specificity (low probability of false alarms). Throughput is also currently defined by these regulations. The certifiable level of throughput with high sensitivity and high specificity is difficult to achieve in systems which must complete the processing of a bag while it is in the scanner, and stop the conveyor if necessary to accomplish that end.
While both the Vivid and Invision Machines are designed to automatically detect explosives, to date the Vivid Machine has not been certified by the FAA. The throughput of the Invision Machine is insufficient because it does not continuously scan bags. The belt is stopped for each bag, and a variable number of slices are acquired for each bag depending upon the contents of the bag. Therefore, it is impossible to reliably predict throughput of the machine.
It is an object of the present invention to overcome the infirmities of these prior art systems.
A more specific object of the present invention is to provide an automatic X-ray detection system.
Another object of the present invention is to provide an improved automatic X-ray detection baggage scanning system capable of acquiring sufficient data at a desired data rate while an item passes through the system so as to eliminate the need to take a variable number of slices so that the conveyor can continuously transfer bags through the system without stopping the conveyor.
Another object of the present invention is to provide an automatic X-ray detection system capable of reliably providing a certifiable level of throughput with high sensitivity and high specificity.
And another object of the present invention to increase the throughput, while reducing the overall costs of an automatic X-ray detection system.
It is yet another object of the present invention to provide an improved system architecture for use in such systems.
It is still another object of the present invention to provide an improved software architecture for an automated X-ray baggage scanning system.
It is still another object of the present invention to provide improved data processing techniques to meet certification requirements and yet use known multi-processor systems for processing the data.